1. Field of the invention
This invention relates in general to material dispensing devices and in particular to a new and useful device for dispensing a toner material in a copying apparatus.
2. DESCRIPTION OF THE PRIOR ART
In electronic copying apparatus an electrostatic latent image is formed by exposing a photosensitive surface to an optical image of a graphical material to be duplicated in the exposing step and it is developed into a visible image by using a developing agent which is a mixture of toner powder and carrier particles. The production of a visible image of uniform density makes it necessary to maintain the ratio of the toner to the carrier in a predetermined range. Since the toner is consumed by adhering to the electrostatic latent image in the developing step it is necessary to provide means for suppling the toner to the developing surface during developing. In the known types of toner dispensing apparatus which are used with copiers the toner is dispensed from the lower end of a supply container through a cylindrical passage which contains a rotatable slotted roller or brush roller. A disadvantage in this construction is that the material is dispensed in unequal quantities throughout the entire length of the rollers and in addition the characteristic of the toner and the feeding thereof is uneven. This condition is aggravated by the addition of toner to the supply container and the tendency of the toner to collect into compact masses. When the toner is not dispenzed smoothly and uniformly along the entire length of the discharge opening there is a tendency for the portion remaining in the container to form into compact masses on each container wall and the material becomes stuck at such locations. In order to avoid this it has been proposed to provide means for vibrating the supply container in order to cause the material to become dislodged from the walls. Such an arrangement however is expensive and is difficult to maintain in operating condition.